1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to searching for rights objects stored in a portable storage device using an object identifier.
2. Description of Related Arts
Recently, digital rights management (DRM) is being actively researched, developed, and used in commercial services. DRM needs to be used in commercial services because of the following various characteristics of digital content. Unlike analog data, digital content can be easily copied without loss, reused, processed and distributed. However, large amounts of money, labor, and time are needed to produce digital content. When the digital content is copied and distributed without permission, the producer of the digital content loses profit, and the motivation to produce is reduced. As a result, the development of digital content businesses may be hampered.
Several efforts have been made to protect digital content. Conventionally, digital content protection has concentrated on preventing non-permitted access to digital content, and permitting only people who have paid fees to access the digital content. However, when a person who has paid the fees intentionally distributes the digital content to other people, these people can use the digital content without paying. To solve this problem, DRM was introduced. In DRM, anyone is allowed to freely access encrypted digital content, but a license, referred to as a rights object, is needed to decrypt and execute the digital content. Accordingly, the digital content can be more effectively protected by using DRM, as compared to the conventional method.
A portable storage device is a connectable/disconnectable device such as a portable phone, a computer, or a digital camera that is portable and that can store data of various types. The portable storage device includes a storage space for storing data, and a portion performing operations and control. A multimedia card (MMC) is a portable storage device which stores multimedia data to be used for various types of digital equipment, overcoming limitations of conventional hard disks and compact disks. The MMC also includes an operational unit that is not included in conventional storage media, thereby having the ability to perform control. Recently, a security function was added to the MMC, thereby developing a secure MMC that protects the digital content from being copied during storage and transmission. With the development of the secure MMC, rights management of digital content has become possible. Hereinafter, digital equipment such as a digital camera, a portable phone, a computer and a digital camcorder will be collectively referred to as a “host device.”
Recently, memory cards including a flash memory have become popular portable storage devices. They differ from a dynamic random access memory (DRAM) and a synchronization random access memory (SRAM) in that they can maintain data without a supply of power. However, a disadvantage of these devices is that they are slower at reading and writing data than DRAMs and SDRAMs.
A rights object stored in a portable storage device is information to be referenced whenever content is reproduced, which requires repetitive reading, writing and modifying operations. To effectively perform these repetitive operations, it is necessary to reduce time consumed in searching for a specific rights object.
A conventional method of providing a cache function through an SRAM to thereby increase input/output speeds of a memory card has been presented in Korean Unexamined Patent Publication No. 10-2002-0020104. In the conventional method, the SRAM is initialized when the memory card is connected to a digital device and thereafter functions as a cache memory storing specific data therein during read and write operations, thereby increasing input/output speed.
The conventional method may increase the input/output speed when searching for data that has been previously searched for, but it cannot decrease the inherent delay caused in data searching.
In particular, since the portable storage device storing rights objects therein under the DRM system repeatedly performs input/output operations for a specific rights object and searches for rights objects, there is a need for a method to improve the speeds of the inputting, outputting, and searching operations.